Aromatic highly condensed

Difluoronaphthalene [315-52-6] is prepared from 4-fluoro-l-naphthylarnine by the Balz-Schiemann reaction. 1,4-Difluoronaphthalene is used in chemical carcinogenesis studies as a synthon for highly condensed difluoro—polycycHc aromatic hydrocarbons (273). 

The effect of conversion on the structure of an asphaltene molecule has been reported to depend on the operating conditions and on the presence or not of a catalyst. The effect of thermal processing reaction of a vacuum residue resulted in the selective cracking of the aliphatic or naphthenic side chains of the molecule, leaving the highly condensed aromatic core structure almost intact (see Fig. 16) [116]. 

Partial hydrogenation of polycyclic aromatics can also be accomplished with [Co(CO)4]2 under hydroformylation conditions.24,26 Isolated benzene rings are generally resistant under these conditions. Polycyclic aromatics, consequently, are only partially hydrogenated174 [Eq. (11.38)], and highly condensed systems usually form phenanthrene derivatives ... 

By varying the substituents on the orange parent substance 19, particularly in the positions para to the imino groups, its color can be modified. Red to red-violet shades result when X=OH or O R, and blue colors when X=NH2 or NHR. A blue shade also results if the external phenyl groups of the dioxazine system are part of an annulated and highly condensed aromatic ring system, for example, pyrene (C.I. Direct Blue 109, [33700-25-3]). 

Probably the same reaction, the dehydrogenation, condensation, and irreversible adsorption of highly condensed aromatic hydrocarbons, causes the loss of activity of the WS2 catalyst when used at pressures well below 200 atm. As an example (20), in experiments with a paraffin-base petroleum-oil fraction boiling between 200° and 325°C. the results in the accompanying tabulation were obtained ... 

The six sample series studied exhibited progression from a highly functional aromatic structure to one that displays little functionality. The aromatic band in PSMC-53 spans a chemical shift range characterized primarily by simple aromatic and condensed aromatic ring systems with significantly less functionality than observed in lower rank samples in this series. 

It seems that the medium volatile coal remains unchanged. Cleaving and condensing effects probably balance each other. The extractablllty of the low volatile coal Is however Increased, especially by hydrogen fluoride at 80 C. The semi-anthracite Is essentially unaffected by such treatements because of Its highly condensed aromatic structure. 

The average molecular parameters obtained from the and C NMR data are summarized in Table V. The rather low (H/C)ar ratios (0.38-0.58) indicate the presence of aromatic rings which are either highly condensed and/or substituted with alkyl substituents. For most samples, 1-5 aromatic rings per average molecule could be inferred from the data. However, the Monterey SRC Fraction 30 exhibits the lowest aromatic ratio suggesting an even greater number of condensed aromatic... 

The reason for the differences In the properties of the two sets of coked catalysts may lie in the nature of the feed. The AN feed is entirely aromatic, which would likely lead to a highly condensed aromatic-like coke. On the other hand the VGO feed hafi a relatively low aromatic content (about, which may be expected to give a less compact coke. The VGO feed also contains appreciable nitrogen. The N-compounds would adsorb more strongly than aromatics aiid could serve as coking nucleation centers, so that the coke could tend to build up closer to pore mouths. 

An experimental study has shown that the addition of quinoline and phenanthrene to a n-hexadecane feedstock in MAT experiments leads to a loss in overall conversion. Characterisation of the coke from this feedstock, indicates that the initial coke formed is highly aliphatic in nature. Quinoline acts primarily as a catalyst poison but also favours coke formation. Solid state C NMR was used to characterise the coke formed from a heavy oil feedstock on demineralisation of the deactivated catalyst. The coke was now observed to be aromatic and highly condensed and it was possible to achieve this characterisation at realistic coke levels of ca. 1% without employment of large coke deposits as hitherto. 

In the pyrolysis of polyethylene at 810°C, the low boiling fraction contains, apart from benzene, more than 10 wt-% of cyclo-pentadiene. If benzene-rich first runnings and last runnings (toluene-rich) are removed, one can obtain a fraction containing about 98 wt-% of benzene. The main constituents of the high boiling fractions are naphthalene, methylnaphthalene and indene, as well as highly condensed aromatics. 

Complex reactions occur during high-temperature treatment of aromatic hydrocarbons. An important class of reactions involve the cyclization and condensation of simpler PAHs to form highly condensed polycyclic compounds. This is discussed more fully by Zander (1995). 

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